Elastomeric Couplings
Elastomeric Couplings
(OP)
All,
I have an application where we are experiencing premature pump / motor coupling failures. We are using a Hytrel elastomeric toothed, shear, sleeve and flange coupling. The motor is equipped with a VFD that operates in steps starting at 3600rpm then steps down to 2700rpm then to 1800rpm. The motor nameplate Hp is 60 but never gets over 45 during operation.
We had a recent coupling failure where the elastomeric coupling melted. I have read that VFD’s will produce torsional pulses at low speed greater than those at high speeds. I have also read that heat can be generated through the effects of vibration and hysteresis of the elastomeric coupling sleeve.
Is it possible that when the VFD is operating at the lower speed the vibratory pulses are generating enough vibration for hysteresis heat to be an issue?
Any feedback is greatly appreciated.
I have an application where we are experiencing premature pump / motor coupling failures. We are using a Hytrel elastomeric toothed, shear, sleeve and flange coupling. The motor is equipped with a VFD that operates in steps starting at 3600rpm then steps down to 2700rpm then to 1800rpm. The motor nameplate Hp is 60 but never gets over 45 during operation.
We had a recent coupling failure where the elastomeric coupling melted. I have read that VFD’s will produce torsional pulses at low speed greater than those at high speeds. I have also read that heat can be generated through the effects of vibration and hysteresis of the elastomeric coupling sleeve.
Is it possible that when the VFD is operating at the lower speed the vibratory pulses are generating enough vibration for hysteresis heat to be an issue?
Any feedback is greatly appreciated.





RE: Elastomeric Couplings
Variable speed drives do put out additional frequencies that can affect torsional conditions. With the particular type of coupling you describe, I would find it believable that the torsional pulsations are generating additional heat. I would prefer a different type of coupling. My first choice would be a metallic flexible element (disk-pack) type coupling. This would be much stiffer and could transmit the torsional pulsations to the driven equipment. If an elastomeric coupling was necessary, I would prefer a torus (rubber dough-nut) or a jaw-type with a star pattern element.
Someone with an electrical background may also be able to recommend a change to the VSD to reduce the torsional pulsation. I have no expertise in this area and simply know enough to know that this can be minimized.
Johnny Pellin
RE: Elastomeric Couplings
one other consideration is to determine if the coupling is sized properly i.e. HP/RPM. At lower speeds the coupling may be undersized and not rated for that speed of operation. you may need to resize your coupling. Also, check your coupling service factor and see if there is any wiggle room.
RE: Elastomeric Couplings
I would change to membrane coupling selected on 60 HP @ 1800 rpm with a 1.5 SF
RE: Elastomeric Couplings
RE: Elastomeric Couplings